A liquid crystal panel in a Thin Film Transistor-Liquid Crystal Display (TFT-LCD) is mainly composed of an array substrate, a color film substrate and a liquid crystal layer located between the array substrate and the color film substrate, and two polarizers with two polarization directions completely perpendicular to each other are arranged on the array substrate and the color film substrate, respectively. When the TFT-LCD operates, light rays emitted by a backlight irradiate the array substrate, the transmittance of the light rays through the liquid crystal layer and the color substrate is determined according to image data inputted to the TFT-LCD, and the display panel may display different color grade according to different transmittance and thereby display an image.
On the color film substrate there are regularly arranged color resins of three colors red, green, and blue (RGB), which correspond to sub-pixel units of three colors RGB, respectively, and three sub-pixel units of different colors constitute a pixel. The backlight when the TFT-LCD operates is of white light, which is usually formed by mixing the three primary colors RGB, the white light becomes linearly polarized white light after passing through the polarizer at the array substrate side, and the polarization direction of the linearly polarized light after passing through the liquid crystal layer is affected by the thickness of the liquid crystal layer and the liquid crystal deflection angle. Generally, the structures of pixel electrodes or the common electrode corresponding to three RGB sub-pixel units are identical and the voltages thereof are equal, such that the liquid crystal deflection angles of the three RGB sub-pixel units are identical. Therefore, after the white light rays pass through the liquid crystal layer of which the thickness of the liquid crystals is equal and of which the liquid crystal deflection angles are identical, since the polarization angles of the light of three colors RGB which constitutes the white light rays are different, and then the three kinds of light rays pass through the polarizer at the color film substrate side, such that the transmittance of the three kinds of light is unequal, such a phenomenon will result in inequality of the light intensity ratios of the outgoing light of the three sub-pixel units, in turn result in that there is a color cast between the color manifested by mixing the three kinds of outgoing light and the color of white light, and that there is a difference between a displayed image and an original image due to the effect of the color cast when displaying an image, thereby affecting the display effect.